CN110691923A

CN110691923A - Vibration damping method and vibration damper assembly for semi-submerged or submerged structures

Info

Publication number: CN110691923A
Application number: CN201880035409.3A
Authority: CN
Inventors: E·伦德; H·B·约翰森; T·伦德奎斯特; L·奥德伦德
Original assignee: Momentum Technologies AS
Current assignee: Momentum Technologies AS
Priority date: 2017-04-07
Filing date: 2018-03-06
Publication date: 2020-01-14
Anticipated expiration: 2038-03-06
Also published as: EP3607221B1; AU2018249260A1; US20190338482A1; EP3607221A4; US11492773B2; NO20170585A1; AU2018249260B2; EP3607221A1; CN110691923B; WO2018186746A1; NO343819B1

Abstract

The invention relates to a vibration damping method and a hydrohook-supported vibration damper assembly (100) for semi-submerged or submerged structures (200, 210, 220, 300) based on supporting a hydrodynamic additional mass (m) by means of the hydrohook-supported vibration damper assembly (100)_add) Separate from the semi-submerged or submerged structure (200, 210, 220, 300), the hydro-hook supporting vibration damper assembly having spring and/or damper characteristics; and adding hydrodynamic additional mass (m)_add) Used as a hydro hook to support a reaction mass in a vibration damper assembly (100).

Description

Vibration damping method and vibration damper assembly for semi-submerged or submerged structures

Technical Field

The present invention relates to a vibration damping method for a semi-submerged or submerged structure according to the preamble of claim 1.

The invention also relates to a hydro hook supported vibration damper assembly for semi-submerged or submerged structures according to the preamble of claim 11.

More particularly, the present invention relates to a vibration damping method and a hydro-hook supported vibration damper assembly for semi-submerged or submerged structures that utilizes the hydrodynamic mass that all semi-submerged or submerged structures experience to reduce vibration and thus reduce their chances of fatigue failure.

Background

Many submerged and semi-submerged marine structures experience problems of dynamic motion, shock and vibration causing fatigue. The oil and gas industry is extending the life of old reservoirs, increasing the flow rate in old pipelines beyond their original expiration date. This increases the chance of hydrocarbon leakage, which results in significant production losses, substantial environmental leakage, maintenance costs, and a loss of life risk.

Vibration and fatigue are not only associated with the oil and gas industry, but other renewable energy structures (e.g., wind or tidal energy, marine vessels, and fish farms) can also encounter many of the same problems.

Marine structures can withstand many types of dynamic forces: semi-submerged structures may be subjected to wind, wave and ocean current loads. Submerged pipes may also be subjected to internal forces transmitted from the mechanical equipment through the structure, or generated by fluid flowing through the pipe or sound in the pipe.

Common to many marine structures is the difficulty in inspecting and maintaining underwater systems. Thus, the marine structure must be strong, typically requiring a service life of over 20 years. In this time frame, the structure must withstand the vibrations caused by all the dynamic forces it is subjected to.

There are many different techniques available for controlling vibration. They can be classified as active or passive systems.

Active systems use energy to reduce vibrations and typically have electronic vibration controllers that use feed-forward and/or feedback to control actuators that counteract motion. Passive damping systems utilize friction, viscous or magnetic or other types of losses to dissipate energy without the use of an external power source.

The use of active systems underwater in the past has not been known, and passive vibratory systems have also rarely been used in underwater systems.

Examples of such systems are viscous dampers and reaction mass dampers that can act on one or more shafts. Viscous dampers are basic components in mechanical lumped element models with two connection points, typically where the vibrating structure is connected to one end and the foundation to the other. The dashpots or shock absorbers of the automobile behave like viscous dampers.

The reactive mass damper uses the inertia of the secondary mass to counteract the motion of the vibrating structure. Both passive and active systems exist. Passive systems are known as tuned mass dampers, harmonic absorbers, tuned absorbers or Lanchester dampers. The reaction mass of the passive system is connected to the slotted spring and damper element of the vibrating structure to generate a reaction force. The dissipation and transfer of mechanical energy combine to reduce vibrations in the main system.

For submerged applications, a disadvantage of the prior art solutions is that they are not suitable for low frequencies.

The prior art solutions also have the following drawbacks: they are only capable of damping vibrations in a relatively narrow frequency range.

The prior art solutions also have the following drawbacks: they need to be arranged on the foundation on one side thereof.

The prior art is also disadvantageous in that if more than one damping system is used, they will interact/counteract each other's functions.

Another disadvantage of prior art solutions is that they introduce large gravitational loads into the structure.

The prior art solutions also have the following drawbacks: they operate underwater in a vertical or horizontal direction and are arranged to attenuate transient or harmonic forces.

Another disadvantage of the prior art is that they comprise many mechanical parts which are prone to wear.

Another disadvantage of the prior art reaction mass dampers is that they are arranged for reducing the mechanical response, but not for handling external forces, i.e. forces from the environment.

Disclosure of Invention

It is a primary object of the present invention to provide a vibration damping method and a hydro-hook supported vibration damper assembly for semi-submerged or submerged structures that partially or fully addresses the shortcomings of the prior art.

It is an object of the present invention to provide a vibration damping method and a hydro-hook supported vibration damper assembly for semi-submerged or submerged structures that utilizes a hydrodynamic mass to reduce vibration in the semi-submerged or submerged structures.

It is a further object of the present invention to provide a vibration damping method and a hydro-hook supported vibration damper assembly for semi-submerged or submerged structures that is capable of separating a hydrodynamic additional mass from the semi-submerged or submerged structures by at least one spring element and/or damping element.

It is an object of the present invention to provide a vibration damping method and a hydraulic hook support vibration damper assembly for semi-submerged or submerged structures, implemented as tuned mass dampers or tuned absorbers, or as Lanchester dampers.

It is an object of the present invention to provide a vibration damping method and a hydro-hook supported vibration damper assembly for semi-submerged or submerged structures that can reduce vibration over a wide frequency range.

It is an object of the present invention to provide a vibration damping method and a hydro-hook supported vibration damper assembly for semi-submerged or submerged structures, which is also used for low frequencies.

It is another object of the present invention to provide a vibration damping method and hydraulic hook support vibration damper assembly for semi-submerged or submerged structures that does not require a foundation.

It is an object of the present invention to provide a vibration damping method and a hydraulic hook support vibration damper assembly for semi-submerged or submerged structures which does not interact/counteract the function of other damping systems for connection with the semi-submerged or submerged structure to which the hydraulic hook support vibration damper assembly according to the present invention is arranged.

It is another object of the present invention to provide a vibration damping method and a hydro hook support vibration damper assembly for semi-submerged or submerged structures that has a large vibration damping capacity due to the large mass ratio of the sea floor.

It is an object of the present invention to provide a vibration damping method and a hydraulic hook support vibration damper assembly for semi-submerged or submerged structures that does not introduce large gravitational loads to the semi-submerged or submerged structures.

It is a further object of the present invention to provide a vibration damping method and a hydro-hook supported vibration damper assembly for semi-submerged or submerged structures operating underwater in both vertical and horizontal directions.

It is an object of the present invention to provide a vibration damping method and a hydro-hook supported vibration damper assembly for semi-submerged or submerged structures that can be implemented to provide a robust design with few mechanical components.

It is an object of the present invention to provide a vibration damping method and hydraulic hook support vibration damper assembly for semi-submerged or submerged structures for transient and harmonic forces.

It is yet another object of the present invention to provide a vibration damping method and a hydro-hook support vibration damper assembly for semi-submerged or submerged structures that is capable of mitigating mechanical responses caused by internal and external forces.

It is an object of the present invention to provide a vibration damping method and a hydraulic hook support vibration damper assembly for a semi-submerged or submerged structure, which can be implemented as an active or passive hydraulic hook support vibration damper assembly.

It is another object of the present invention to provide a hydro hook support vibration damper assembly that can provide buoyancy to a semi-submerged or submerged structure in addition to the above objects.

It is an object of the present invention to provide a vibration damping method and a hydraulic hook support vibration damper assembly for a retractable semi-submerged or submerged structure.

It is an object of the present invention to provide a vibration damping method and a hydro-hook supported vibration damper assembly that reduces vibration in six degrees of freedom, thereby effectively reducing the number of dampers required for a given vibration problem.

It is an object of the present invention to simplify and enhance the robustness of the tuning process of a hydro hook supported vibration damper assembly.

Other objects of the invention will appear from the following exemplary description, from the claims and from the drawings.

Description of the invention

A vibration damping method for a semi-submerged or submerged structure according to the invention is disclosed in claim 1. Preferred features of the method are disclosed in the dependent claims.

A hydro hook supported vibration damper assembly for a semi-submerged or submerged structure according to the present invention is disclosed in claim 11. Preferred features of the hydro-hook supported vibration damper assembly are disclosed in the dependent claims.

The complex motion of a vibrating structure is difficult to understand by mere visual observation, as shown in fig. 1, which is a schematic diagram of a vibrating elongated structure and its frequency response (time domain in air). As is well known, this motion can be described as a superposition of multiple single-frequency motions, called eigenmodes/natural modes, as shown in fig. 2, which shows the eigenmodes of the vibrating elongated structure of fig. 1. When a force with a single frequency corresponds to the eigenfrequency/natural frequency of an eigenmode, resonance occurs, which is a large amplification of the vibration at locations where the eigenmode has a large motion, called anti-nodes. The vibration of this particular eigenmode will be lower than the vibration of the eigenfrequency for all other forcing frequencies, for example as shown in fig. 3 for the vibrating elongated structure shown in fig. 1 and 2. For a given elongated structure, the observed vibration will be the sum of the motions of all eigenmodes. The spectrum of a point along the elongated structure will be further given by the sum of the spectra of each eigenmode.

It is further known that the motion of each eigenmode can be described mathematically as being represented by an equivalent mass m when observing a point along the vibrating elongated structure_eqSpring k and damper c as shown in fig. 4, which shows a schematic diagram of the lumped mass system. Equivalent lumped parameters can be extracted from a continuous system by measurement or simulation.

The vibration response of this simple one degree of freedom system when the mass is subjected to harmonic vertical forces is given by:

where x is the vibration amplitude, F is the harmonic force amplitude, k is the stiffness coefficient, m_eqIs the mass, c is the damping coefficient, ω is the rotation frequency, and j is the imaginary unit of the complex number.

The vibration amplitude is given by:

if the damping coefficient is zero and the forcing frequency is

The vibrational response of the system will theoretically reach infinity, where ω is the angular frequency [ rad/s ]]F is the frequency [ Hz]. This is called resonance. It is also noteworthy that if c/m_eqWhen the ratio is low enough and the stiffness coefficient is zero, the system is less likely to resonate, such as a system consisting of only a mass and a damper.

It is well known that when the same continuously vibrating elongated structure is immersed in a liquid, such as water, the structure dynamics will change due to the interaction with the liquid. This field of dynamics is called fluid dynamics.

The continuous system can be broken down into a set of similar pattern shapes and the overall response can be described as a superposition of patterns, similar to an elongated structure in air (fig. 2). The response at points along the elongated structure can also be decomposed into a superposition of eigenmode responses each as a lumped mass representation with a given frequency spectrum. The main difference with air is that hydrodynamic effects change the parameters of the model. For low viscosity liquids (e.g., water), the additional damping coefficient is negligible compared to air. On the other hand, for elongated structures immersed in water, the additional mass will be large. This additional mass is referred to as the additional mass or hydrodynamic additional mass and can be considered as an additional mass layer around the elongated structure when it vibrates in water, as shown in fig. 5, which is a schematic diagram of a pipe dynamics model.

The lumped mass representation of points along the elongated structure can be represented as the original representation of the additional mass directly connected to the equivalent mass previously described, as shown in fig. 6, which is a schematic diagram of an immersed lumped mass system.

The hydrodynamic additional mass effect of liquids is troublesome for structures that are prone to vibration. The vibration response will be higher and it will be more difficult to suppress vibrations by mitigation techniques. The former can be seen in the expression of the point response of each eigenmode:

wherein m is_eqIs the equivalent structural mass, m_addIs a hydrodynamic mass. The denominator will follow m_addIs increased and contracted, thereby increasing the vibration amplitude x.

In accordance with the present invention, a method and hydraulic hook support vibration damper assembly are provided that utilize a hydrodynamic additional mass as a reaction mass in the hydraulic hook support vibration damper assembly to exhibit spring and/or damper characteristics.

The term structure as used in the further description includes, in addition to the primary structure, an extension of the structure, a support structure for the structure, or a hydro-hook support vibration damper support structure for arranging the hydro-hook support vibration damper assembly to the structure, extension of the structure, or support structure for the structure.

The method and the hydrohook-supported vibration damper assembly according to the invention are based on the separation of the hydrodynamic additional mass from the semi-submerged or submerged structure by means of at least one spring element and/or damper element. In this way, the hydrodynamic additional mass can be used as a reaction mass in the hydrohook-supported vibration damper assembly, as shown in fig. 7, which is a schematic diagram of the main principle of the hydrohook-supported vibration damper assembly according to the invention. This change turns the hydrodynamic additional mass from a problem to benefit from its use, thus enabling well-known damping techniques to be implemented and customized for use underwater.

The method and the hydrohook-supported vibration damper assembly according to the invention are thus arranged to separate the hydrodynamic additional mass from the semi-submerged or submerged structure by means of at least one spring element, at least one damping element or a combination of these arranged in a damper space partially or fully enclosing the structure, wherein the damper space is provided by an external covering.

The hydro hook supported vibration damper assembly including a spring element with or without a damping element for decoupling the hydrodynamic additional mass may be considered a Tuned Mass Damper (TMD) or tuned absorber, as shown in fig. 8, which is a schematic diagram of an embodiment of a hydro hook supported vibration damper assembly according to the present invention. If the hydrohook-supporting vibration damper assembly includes only at least one damping element, it can be identified as a Lanchester damper, as shown in FIG. 9, which is a schematic diagram of an embodiment of the hydrohook-supporting vibration damper assembly according to the present invention.

In particular, tuned mass dampers have been used to reduce resonance in many applications in high-rise buildings, bridges, power lines, automobiles, and airplanes.

Viscous dampers requiring attachment of both ends of the damper to moving rigid parts, respectivelyOr shock absorber type dampers, the hydro hook supporting vibration damper assembly according to the above embodiment does not require any foundation. Furthermore, as described above, if the composition parameter (m) is correctly tuned/set according to the relevant vibration structure_addC and k), the hydro-hook supported vibration damper assembly according to the present invention will provide significant damping over a wide range of frequencies as compared to an undamped response.

The main advantage of the method according to the invention in the form of a tuned mass damper and of the hydro-hook supported vibration damper assembly is that for a given mass ratio μm_add/m_eqThe damping will be greater than the method and the hydraulic hook supported vibration damper assembly according to the invention in the form of a Lanchester damper, especially for low mass ratios. The mass ratio of the present invention will be greater than 1 in almost any case, which is very large compared to most other structures and applications using a reactive mass damper (TMD or Lanchester). The performance of the method and hydraulic hook support vibration damper assembly according to the present invention in the form of a Lanchester damper will converge towards the performance of a TMD with a high mass ratio.

Thus, the Lanchester damper refers to a reaction mass damper which has no spring element and can damp rotational vibration/motion with at most three degrees of freedom, and the invention should be regarded as a novel damping method; the reaction mass damper without spring elements can provide six degrees of freedom damping by means of a Hydro Hook Support (HHS) vibration damper.

Accordingly, the present invention provides a method and hydraulic hook support vibration damper assembly utilizing a hydrodynamic mass in a reaction mass damper. The method and hydro-hook supported vibration damper assembly according to the present invention has many advantages not found in other conventional dampers.

A major advantage of the method and the hydraulic hook support vibration damper assembly is that the hydraulic hook support vibration damper assembly can be set to have no natural frequencies that would accommodate the detrimental interaction that multiple TMDs may have on the vibrating structure that would also affect the other damper functions. This means that engineering of the hydraulic hook support vibration damper assembly according to the invention will be easier than using TMD, since the function can be almost guaranteed as long as the hydraulic hook support vibration damper assembly is arranged to a part of the vibrating structure. This also means that a smaller number of hydro hooks are required to support the vibration damper assembly to reduce vibrations to acceptable levels.

By the present invention, a method and a hydro hook support vibration damper assembly are provided that provide a solution suitable for low frequency operation. This would be advantageous because most subsea application problems are related to low frequencies and lack the basis for attaching viscous dampers at both ends.

An advantage of the method and the hydraulic hook support vibration damper assembly according to the present invention is that it is capable of damping vibrations over a wide frequency range.

Another significant advantage of the method and hydraulic hook support vibration damper assembly according to the present invention is that no foundation is required.

Another advantage of the present invention over the prior art is that it does not interact/counteract the function of other damping systems for use in conjunction with the structure in which the hydro-hook supported vibration damper assembly according to the present invention is arranged.

Another advantage is that the method and the hydro hook supported vibration damper assembly according to the invention have a great damping capacity due to the large mass ratio of the sea bottom.

An advantage over the prior art is that the present invention does not introduce large gravitational loads into the semi-submerged or submerged structures.

Another significant advantage of the method and hydraulic hook support vibration damper assembly according to the present invention is that it can work both vertically and horizontally under water.

Another advantage of the present invention is that the method and hydro-hook supported vibration damper assembly according to the present invention can be implemented with few mechanical components to provide a robust design.

Another advantage is that the method and hydraulic hook support vibration damper assembly according to the present invention work with both transient and harmonic forces.

A significant advantage of the method and hydraulic hook support vibration damper assembly according to the present invention is also the ability to mitigate mechanical responses caused by internal and external forces.

Another advantage of the method and hydraulic hook support vibration damper assembly according to the present invention is that the hydraulic hook support vibration damper assembly can be implemented as an active or passive hydraulic hook support vibration damper assembly. For underwater/submerged applications, it is generally preferred to use a passive hydro hook to support the vibration damper assembly due to the harsh environment and the lack of an external power source.

A significant advantage of the present invention is that it is not only associated with radial motion, but can also act axially when rotating (twisting) about the longitudinal axis of the semi-submerged or submerged structure and tilting about the longitudinal axis of the semi-submerged or submerged structure. Accordingly, the present invention provides a method and a hydro-hook supported vibration damper assembly having six degrees of freedom.

The hydro hook supported vibration damper assembly according to the present invention is also advantageous in that it can be divided into sections, which can be retrofitted to existing semi-submerged or submerged structures.

Another advantage of the present invention is that it introduces a small amount of stiction, a known problem with semi-submerged and submerged structures.

Another significant advantage of the present invention is that it can absorb harmonics and transient stresses (vibrations and jerks).

Another advantage of the present invention is that it will further work on both linear and non-linear configurations.

The invention is also advantageous in that it provides an extensible solution making it easily adaptable to any structure from small/short structures to very large/long structures.

Another advantage of the present invention is that it can be used to replace other mechanisms for Vortex Induced Vibration (VIV) in semi-submerged or submerged structures, such as spiral ducts and fairings.

An advantage of the present invention is that it can be implemented as adjustable, if desired or required.

Another advantage of the present invention is that it provides a simple and cost-effective solution for implementing a semi-submerged or submerged structure.

Further preferred features and advantageous details of the invention will emerge from the following exemplary description, the claims and the drawings.

Drawings

The invention will be described in more detail below with reference to the accompanying drawings, in which:

figure 1 is a schematic diagram of a vibrating elongated structure and its frequency response,

figure 2 is a schematic diagram showing the eigenmodes/natural modes of the vibrating elongated structure of figure 1,

figure 3 is a schematic diagram of the frequency response at a given location in figure 2,

figure 4 is a schematic diagram of a lumped mass system,

figure 5 is a schematic diagram of a pipe dynamics model,

figure 6 is a schematic diagram of an immersed lumped mass system,

figure 7 is a schematic diagram of the main principle of the hydro-hook supported vibration damper assembly according to the present invention,

fig. 8 is a schematic diagram of a hydro-hook supported vibration damper assembly, which may be considered a tuned mass damper,

fig. 9 is a schematic diagram of a hydro-hook supported vibration damper assembly, which may be considered a Lanchester damper,

figures 10a-b are schematic diagrams of an example of an outer covering of a hydro-hook supported vibration damper assembly according to the present invention,

figures 11a-b are schematic diagrams of another embodiment of a hydro-hook supported vibration damper assembly according to the present invention,

figures 12-15 are schematic diagrams of other embodiments of a hydro-hook supported vibration damper assembly according to the present invention,

fig. 16a-b are schematic diagrams of another embodiment of a hydraulic hook support vibration damper assembly according to the present invention, comprising a plurality of hydraulic hook support vibration damper assemblies arranged to each other in the longitudinal direction of the structure,

fig. 17 is a schematic diagram of a hydro-hook supported vibration damper assembly, divided into a plurality of sections,

figure 18 is a schematic diagram of another embodiment of a hydro-hook supported vibration damper assembly according to the present invention,

figures 19a-d are schematic diagrams of the hydrodynamic additional mass produced in all six degrees of freedom,

figures 20a-e are schematic diagrams of a structure having a hydro hook support vibration damper assembly according to the present invention disposed thereon,

fig. 21a-e are schematic diagrams of another embodiment of a hydro-hook supported vibration damper assembly according to the present invention, arranged to a different structure,

fig. 22a-c are schematic diagrams of another embodiment of a hydro-hook supported vibration damper assembly according to the present invention, arranged to a different structure,

figures 23a-c are schematic diagrams of another embodiment of a hydro-hook supported vibration damper assembly according to the present invention,

figures 24a-c are schematic diagrams of several hydro-hook supported vibration damper assemblies according to the present invention arranged around a structure,

figures 25a-b are schematic diagrams of another embodiment of a hydro-hook supported vibration damper assembly according to the present invention,

25a-b are schematic diagrams of a hydro-hook supported vibration damper assembly according to the present invention arranged as part of a surrounding structure, an

26-28 are schematic diagrams of a hydro-hook supported vibration damper assembly according to the present invention arranged to a structure.

Detailed Description

The hydro-hook support vibration damper assembly 100 according to the present invention may be implemented with many different types of designs, which will be described below.

The reaction mass m can be realized in the following manner_addThat is, the hydro-hook supported vibration damper assembly 100 includes an outer covering 110 that is arranged in partOr all around a portion or section of the

structure

200, 210, 220, 300.

The structure 200 according to the invention is typically a pipeline for subsea use in the oil and gas industry, such as an SCR (rigid or flexible) riser (as shown in fig. 26) (outlet, drilling, production), jumpers, elastic rings, outlets and transport pipelines and pipelines are some examples. Other examples of structures 200 are protruding valves. Other examples of structures 200 may be support structures 220 or structural members (e.g., beams or poles) of semi-submerged or submerged offshore installations, as shown in fig. 20 a-b. The use of a hydraulic hook to support the vibration damper assembly 100 on the extension 210 of the structure 200 is shown in fig. 20c, and an example of the arrangement of the hydraulic hook supported vibration damper assembly 100 onto the support structure 220 is shown in fig. 20 d. An example of an arrangement of a hydro-hook supported vibration damper assembly 100 as an integral design of a structure 200 according to the present invention is shown in fig. 20 e.

The structure according to the present invention may also be a hydro-hook supported vibration damper support structure 300. The hydraulic hook support vibration damper support structure 300 is a solid structure that can be used to position the hydraulic hook support vibration damper assembly 100 outside/distal of the structure to be damped 200, 210, 220 and to transmit vibrations from the

structure

200, 210, 220 to the hydraulic hook support vibration damper assembly 100, as will be discussed in fig. 21a-b, 22a-c and 23 a-b.

The term structure will be used below for the primary structure 200, the extension of structure 210, the support structure of structure 220, and the hydro-hook support vibration damper support structure 300.

These are just some examples of

structures

200, 210, 220, 300 to which the invention is applicable, other examples of which will be discussed below.

Further example descriptions will primarily relate to elongated, primarily tubular structures 200, such as pipes, tubes, pipes or tubes, cables or cable assemblies, wires, chains, and the like, but the invention is not limited to elongated tubular structures, as described below.

The outer cover 110 has a larger circumference than the

structures

200, 210, 220, 300 and is arranged to surround a portion or section of the

structures

200, 210, 220, 300 in its circumferential direction. The outer cover 110 will further exhibit a length in the longitudinal direction of the portion or section of the

structure

200, 210, 220, 300 to provide a damper space 111 between the outer surface of the portion or portion of the

structure

200, 210, 220, 300 and the inner periphery of the outer cover 110.

Thus, the outer covering 110 will provide an enclosure around a portion/section of the

structure

200, 210, 220, 300, but may in some embodiments primarily encompass the

entire structure

200, 210, 220, 300. The following portions of the description will mainly refer to the outer covering 110 surrounding a portion/section of the

elongated structure

200, 210, 220, 300, but other alternatives will also be described.

The outer cover 110 may also be provided with a seal 112 at its ends to seal the

structure

200, 210, 220, 300 and provide a sealed damper space 111 that separates water from the surrounding

structure

200, 210, 220, 300. The seal 112 may for example be a rubber bellows, a sleeve, a gasket, a seal or the like, but may also be a more complex/advanced mechanical solution, as will be apparent to the skilled person.

Thus, as shown in FIGS. 19a-d, hydrodynamic additional mass or additional inertia (reaction mass) is generated in all six degrees of freedom of the outer cover 110. Three translational degrees of freedom, axial (fig. 19b) +2x lateral (fig. 19a), and three rotational degrees of freedom, torsional (fig. 19d) +2x oscillatory (fig. 19 c).

Referring now to fig. 10a-b, there is shown an example of an outer cover 110 for a hydro-hook supported vibration damper assembly 100 according to the present invention. The design of the outer cover 110 may be any design from a simple cylindrical cover to a more advanced design comprising fins 113, grates 114, spacers 115 or other designs arranged to provide a secondary effect to the hydro hook support vibration damper assembly 100 in addition to being an outer cover, i.e. to reduce vortex shedding and vibrations due to external forces, such as Vortex Induced Vibrations (VIV).

Importantly, the geometry/design of the outer cover 110 used has the smallest static coefficient of resistance possible, but the largest dynamic coefficient of resistance. When the static drag coefficient is high, high static forces are generated, which is a common problem for submerged

structures

200, 210, 220, 300 through which large water flows. Thus, with the illustrated design of the outer cover 110 according to the present invention, the stiction is kept to a minimum. When the dynamic drag coefficient is high, a high hydrodynamic mass is produced, which is required for the damper mass and is preferable for obtaining high performance. Calculations performed by the applicant have shown that four small fins 113 extending substantially perpendicular to each other from the outer shroud 110 around the circumference will produce a hydrodynamic mass of about 1.4 times that of a cylinder having the same outer diameter.

It should be mentioned that the shown replacement of the outer cover 110 is only an exemplary embodiment and that the outer cover 110 may differ from this, for example the fins 113 have different shapes and sizes and the number of fins 113 may be higher or lower than in the shown embodiment.

Further, according to the present invention, the damper space 111 may be filled with a material having a density lower than the ambient liquid (water in the example) to provide buoyancy to the

structure

200, 210, 220, 300 requiring neutral or positive buoyancy. The existing buoyancy elements (not shown) of the

structure

200, 210, 220, 300 may also be used as the outer covering 110 of the hydraulic hook support vibration damper assembly 100 according to the present invention, or the hydraulic hook support vibration damper assembly 100 according to the present invention may be used in combination with the buoyancy elements (not shown) of the

structure

200, 210, 220, 300.

According to the present invention, buoyancy may be achieved by: the damper space 111 is filled with air or buoyancy spacers 115 are provided on the outer cover 110, buoyancy in annulus spacers 130 (as shown in fig. 16 a) or in a separate inner layer or spacer 132 (as shown in fig. 16 b), or buoyancy in the outer cover 110.

Reference is now made to fig. 11a-b, which are schematic illustrations of another embodiment of a hydro-hook supported vibration damper assembly 100 in accordance with the present invention. The damping coefficient c may be achieved by a viscous fluid layer 116 located in the damper space 111 between the outer cover 110 and the

structure

200, 210, 220, 300. Different types of fluids, such as bitumen (i.e., asphalt), silicone fluids, or other types of viscoelastic polymers, may be used in the viscous liquid layer 116 if the viscosity is high enough to create the necessary damping. The thickness of the viscous fluid layer 116 should accommodate the full range of motion necessary for the hydro hook to support the vibration damper assembly 100.

Referring now to fig. 12, which is a schematic diagram of another embodiment of a hydro-hook supported vibration damper assembly 100 according to the present invention, an alternative solution to achieve the damping coefficient c is provided for the embodiment of fig. 11 a-b. In the embodiment of the hydro-hook supported vibration damper assembly 100 in fig. 12, the damping coefficient c is obtained by a plate 118 having a high electrical conductivity and a magnet or magnet assembly 117. According to the embodiment shown, the two plates 118 are arranged to extend mainly perpendicularly from the outer periphery of the

structure

200, 210, 220, 300 towards the inner periphery of the outer cover 110 and are spaced apart in the longitudinal direction of the

structure

200, 210, 220, 300, i.e. extend and are spaced apart in the damper space 111, but are not in contact with the outer cover 110. According to the embodiment shown, the magnets or magnet assemblies 117 are arranged to extend mainly perpendicularly from the inner periphery of the outer cover 110 towards the outer periphery of the

structure

200, 210, 220, 300, i.e. in the damper space 111, the magnets or magnet assemblies 117 being arranged to extend between the plates 118. Thus, by using a plate 118 with a high electrical conductivity and a magnet or magnet assembly 117, an eddy current damping element may be provided. The plate 118 may alternatively be arranged to the outer cover 110 and the magnet or magnet assembly 117 arranged to the

structure

200, 210, 220, 300. Furthermore, a plurality of such eddy current damping elements may be arranged spaced apart in the longitudinal direction of the

structure

200, 210, 220, 300 within the damper space 111. The magnet or magnet assembly 117 may, for example, comprise a strong rare earth magnet, and the plate 118 may, for example, be a copper or aluminum plate. When the magnet or magnet assembly 117 is moved close to the plate 118, an alternating current will be generated in the plate 118. The alternating current will produce an alternating magnetic field that will oppose the motion of the magnet or magnet assembly 117, thereby reducing the velocity of the magnet or magnet assembly 117 and thereby introducing damping.

Reference is now made to fig. 13, which is a schematic diagram of another embodiment of a hydro-hook supported vibration damper assembly 100 in accordance with the present invention. According to the invention, by arranging the outer covering 110 to the

structure

200, 210, 220, 300 with fastening means 119, such as wires, chains or the like, a stiffness coefficient k can be achieved for the horizontally vibrating

structure

200, 210, 220, 300, wherein the fastening means 119 are arranged at one end to the

structure

200, 210, 220, 300 and at the other end to the inner circumference of the outer covering 110, wherein the fastening points for the fastening means 119 in the structure 200 and the outer covering 110 are moved in the longitudinal direction of the outer covering 110 in order to provide a swinging movement in this way. By varying the length, i.e., the oscillation, of the fastening device 119, the frequency at which the hydro hook supports the vibration damper assembly 100 may be tuned.

Reference is now made to fig. 14, which is a schematic diagram of another embodiment of a hydro-hook supporting vibration damper assembly 100 in accordance with the present invention. In this embodiment, the seal 112 separating the outer cover 110 from the

structures

200, 210, 220, 300 may also additionally act as a spring element for the hydro-hook supporting the vibration damper assembly 100. According to the present invention, providing the seal 112 with a spring function may be accomplished by forming the seal 112 from an elastomeric material, such as an elastomer/rubber, that is capable of providing the bellows/spacer/sleeve/seal with the necessary stiffness.

Referring now to FIG. 15, there is shown a schematic diagram of another embodiment of a hydro-hook supported vibration damper assembly 100 in accordance with the present invention, which is an alternative embodiment to the embodiment of FIG. 14. In this embodiment, the hydro hook support vibration damper assembly 100 is provided with one or more mechanical springs or spring assemblies 120 extending between the outer periphery of the

structure

200, 210, 220, 300 and the inner periphery of the outer cover 110, disposed in the adhesive layer 116 in the damper space 111.

Referring now to fig. 16a, there is shown another embodiment of a hydraulic hook support vibration damper assembly 100 according to the present invention, wherein a plurality of separate hydraulic hook support vibration damper assemblies 100 are arranged with one another in the longitudinal direction of the

structure

200, 210, 220, 300. According to the present invention, a plurality of hydro hook support vibration damper assemblies 100 may be arranged with one another by an annular spacer 130 that holds the hydro hook support vibration damper assemblies 100 in place in the

structures

200, 210, 220, 300. The annulus spacer 130 is preferably provided with a sliding surface 131 for the hydro hook to support the outer cover 110 of the shock absorber assembly 100. The sliding surface 131 of the annulus spacer 130 may have low friction or high friction. Under high friction, adhesive layer 116 may be replaced by an incompressible fluid such as water. Thus, the sliding surface 131 can be used to provide a desired damping coefficient c for the damper assembly 100. Annulus spacer 130 will further act as a buoyancy element for structure 200.

Reference is now made to fig. 16b, which is a schematic diagram of a modified embodiment of the embodiment shown in fig. 16 a. In the embodiment shown in fig. 16b, an inner layer or longitudinal spacer 132 is disposed between the adhesive layer 116 and the elongated structure 200. This will enable several assemblies of hydro-hook-supported vibration damper assemblies 100 to form a damper unit that is easily retrofitted for semi-submerged or submerged elongated structures 200. The inner layer or longitudinal spacers 132 may further act as buoyancy elements similar to the annulus spacers 130 and the outer shroud 110.

As described above, the adhesive layer 116 in fig. 16a-b may be replaced with a frictional surface, eddy current damping, and/or a spring.

Further, the hydro hook support vibration damper assemblies 100 arranged with one another may be arranged to cover different vibration frequency ranges.

Reference is now made to fig. 17, which is a schematic diagram of another embodiment of a hydro-hook supported vibration damper assembly 100 in accordance with the present invention. The hydro-hook supported vibration damper assembly 100 according to the present invention may also be arranged to be retrofitted to existing

structures

200, 210, 220, 300 by being divided into sections 100a which are interconnected by being provided with a snap or clamp mechanism 140 which can be manipulated by a diver or ROV. This will also enable the sections 100a of the hydro-hook supported vibration damper assembly 100 to be arranged in the circumferential direction of the structure 200 for

large diameter structures

200, 210, 220, 300.

The length of the hydro-hook supported vibration damper assembly 100 according to the present invention can vary from very short lengths less than the diameter of the

structures

200, 210, 220, 300 to very long lengths. The hydro hook support vibration damper assembly 100 according to the present invention should allow the vibrating

structure

200, 210, 220, 300 to move freely without contacting the outer cover 110. The mass ratio will not be affected by the length, since the ratio is given by the cross-sectional geometry of the outer cover 110 compared to the mass per length characteristic of the vibrating

structure

200, 210, 220, 300.

Due to the separation of the hydrodynamic mass from the vibrating

structure

200, 210, 220, 300 and the use of ambient water instead of the metal mass typically used in conventional TMDs, the hydro hook support vibration damper assembly 100 according to the present invention will not add hydrodynamic or gravitational loading to the

structure

200, 210, 220, 300.

The hydro hook support vibration damper assembly 100 according to the present invention will maintain the outer shroud 110 near neutral buoyancy, creating a hydrodynamic reaction mass effect. This will prevent the outer covering 110 from always being in contact with the

vibration structure

200, 210, 220, 300, allowing the hydro hook support vibration damper assembly 100 according to the present invention to be oriented in both vertical and horizontal directions.

The outer cover 110 for the hydro-hook supported vibration damper assembly 100 according to the present invention need not be made of any particular material, but plastic or composite materials are most likely due to their near neutral buoyancy and ease and cost of manufacture. The material of the outer cover 110 may be rigid or flexible and have additional damping. Reference is now made to fig. 18, which is a schematic diagram of another embodiment of a hydrohook-supported vibration damper assembly 100 according to the present invention, which is arranged to introduce stiffness and/or damping in series with respect to the

spring elements

112, 119, 120 and/or damping

elements

116, 117, 118 described above. This may be achieved according to the invention by the outer cover 110 being made of a rigid or flexible material.

Reference is now made to fig. 21a-b, which are schematic illustrations of another embodiment of the present invention in which a hydraulic hook support vibration damper assembly 100 according to the present invention is arranged onto a hydraulic hook support vibration damper support structure 300. The hydro-hook supporting vibration damper support structure is arranged to the

structure

200, 210, 220 to be damped. In this embodiment, the solid support structure 300 is formed by a clamp assembly comprising two clamps 301 for placement to the

structures

200, 210, 220 and further comprising a rod 302 extending from the respective clamp 301 and a rod 303 connecting the rods 302, the hydraulic hook support vibration damper support structure 300 positioning the hydraulic hook support vibration damper assembly 100 external/distal to the

structures

200, 210, 220, wherein the hydraulic hook support vibration damper support structure 300 transmits vibrations transmitted from the

structures

200, 210, 220 to the hydraulic hook support vibration damper assembly 100 through the clamps 301 and

rods

302, 303. In the illustrated example of fig. 21a, the hydro-hook support vibration damper assembly 100 encloses a rod 303, which rod 303 is rigidly connected to the structure to be damped 200, 210, 220 by a rod 302 and a clamp 301. It should be noted that the above-described embodiment will also be applicable to this embodiment. The

structures

200, 210, 220 in fig. 21a-b may be, for example, transport pipes or sea cables. An example of a hydro hook supported vibration damper assembly 100 based on this principle, which is arranged on a

support structure

200, 210, 220 in a subsea application, is shown in fig. 21 c.

As shown in fig. 21b, the

rods

302 and 303 may be arranged at different angles relative to each other, such that the hydro-hook support vibration damper assembly 100 may be arranged in different positions relative to the

structure

200, 210, 220, for example to both sides of a pipe bend.

An example of arranging the hydraulic hook-supported vibration damper assembly 100 onto a structure 200 in the form of a jumper and a flexible ring is shown in fig. 21d-e, where fig. 21d shows an example where the hydraulic hook-supported vibration damper assembly 100 is arranged to surround a portion/section of the jumper and the flexible ring, and fig. 21e shows an example of arranging the hydraulic hook-supported vibration damper assembly 100 onto the jumper and the flexible ring using the hydraulic hook-supported vibration damper support structure 300 described above.

Referring now to fig. 22a-c, there is shown an example of another embodiment of a hydrohook-supported vibration damper support structure 300 in the form of a rod 302 or bar secured to the

structure

200, 210, 220, wherein the hydrohook-supported vibration damper assembly 100 arranges the rod 302 or bar as described above. Figure 22a shows the damping of the blowout preventer stack, while figures 22b-c show the damping of the support structure for the offshore wind turbine, which is fixed to the seabed (struts, tension legs) and floating/semi-submersible, respectively.

Reference is now made to fig. 23a-b, which show a schematic diagram of another embodiment of a hydrohook-supported vibration damper support structure 300 and a hydrohook-supported vibration damper assembly 100 for arrangement onto a

structure

200, 210, 220 to be damped in accordance with the present invention. In this embodiment, the hydro-hook supported vibration damper assembly 100 is substantially the same as the embodiment described above with some modifications, which will be discussed below. In the embodiment shown in fig. 23a, the hydrohook-supporting vibration damper assembly 100 is provided with a central buoyancy module 150 arranged to provide neutral buoyancy to the hydrohook-supporting vibration damper 100. The hydro hook support vibration damper assembly 100 is provided with a reservoir 160 containing the viscous fluid 116 on each side of the central buoyancy module 150. In this embodiment, the hydrohook-supporting vibration damper support structure 300 does not include a rod 303 extending through the hydrohook-supporting vibration damper assembly 100, but rather includes two rods 303a extending into the container 160 from each side and in contact with the viscous fluid 116.

Thus, in this embodiment, the hydraulic hook support vibration damper assembly 100 only surrounds the end portion of the rod 303a of the hydraulic hook support vibration damper support structure 300. Also, this embodiment may use the above-described embodiment for the hydro-hook supported vibration damper assembly 100.

Further, the function of this embodiment is very similar to the hydraulic hook support vibration damper assembly 100 including the bar 303 passing through the entire hydraulic hook support assembly 100, but now the damping is distributed over two bars 303a, rather than along the entire bar 303. An advantage of this embodiment is that the damping characteristics for the rotational movement will be easier to separate and a simpler and robust design will be enabled which is easier to manufacture. A further advantage is that since less drainage area uses a higher viscosity viscous fluid that will make it more susceptible to leakage, separate buoyancy modules can be implemented and the axial and radial damping parameters can be controlled and tuned by using different geometry rods 303 a.

In fig. 23b an alternative embodiment to the embodiment in fig. 23a is shown, wherein the container 160 is sealed and a rod 303a extending into the container 160 is provided with a joint 170 for connection to the hydrohook-supported vibration damper support structure 300 at the outer surface of the container 160, and it is also possible to use an intermediate rod portion 303b connected to the rod 302 via the joint 170. This embodiment will work as the embodiment described in fig. 23b, but will provide a simpler arrangement in place for the

structures

200, 210, 220 to be damped.

Reference is now made to fig. 24a-c, which are schematic illustrations of several hydro-hook supported vibration damper assemblies 100 arranged into the

same structure

200, 210, 220. In fig. 24a an embodiment as described above is shown, wherein one hydro hook supported vibration damper assembly 100 is arranged to the

structure

200, 210, 220 by means of a hydro hook supported vibration damper support structure 300. In fig. 24b an embodiment is shown wherein two hydro hook supported vibration damper assemblies 100 are arranged to the

same structure

200, 210, 220 by means of a hydro hook supported vibration damper support structure 300, wherein the hydro hook supported vibration damper assemblies 100 are arranged on opposite sides of the

structure

200, 210, 220. In fig. 24b an embodiment is shown wherein three hydro-hook supported vibration damper assemblies 100 are arranged around the circumference of the

same structure

200, 210, 220 by means of a hydro-hook supported vibration damper support structure 300, wherein the hydro-hook supported vibration damper assemblies 100 are distributed along the circumference of the

structure

200, 210, 220, in this example they are positioned at about 120 degrees in relation to each other.

Reference is now made to fig. 25a-b, which are schematic illustrations of another embodiment of a hydro-hook supported vibration damper assembly 100 in accordance with the present invention. In this embodiment, the outer cover 110 is provided with fins 113 extending in the longitudinal direction of the structure 200 or the vertical direction of the structure 200. The fins 113 are not limited to the illustrated embodiment, and may extend in both vertical and horizontal directions and exhibit other shapes or patterns as described above. In this embodiment, the outer surface 201 of the structure 200 will serve as the inner restraint of the hydro-hook supported vibration damper assembly 100, and wherein the outer cover 110 assumes a shape corresponding to the outer surface 201 of the structure 200. The outer cover 110 is further provided at its end with a seal 112 to seal the outer surface 201 of the structure 200 and provide a sealed damper space 111 between the outer surface 201 of the structure and the outer cover 110, which is separated from water and can be filled with the viscous fluid 116. The seal 112 may for example be a rubber bellows, a sleeve, a gasket, a seal or the like, but may also be a more complex/advanced mechanical solution, as will be apparent to the skilled person. The seal 112 may further be arranged to secure the hydro-hook support vibration damper assembly 100 to the outer surface 201 of the structure, or the outer cover 110 may be arranged to the outer surface 201 of the structure 200 by suitable fastening means (not shown). Thus, this embodiment of the hydro-hook supported vibration damper assembly 100 provides a solution in which the hydro-hook supported vibration damper assembly 100 may be used as a covering, coating, or cladding for the outer surface 201 of the structure 200. In an alternative embodiment, the hydro-hook supported vibration damper assembly 100 includes a container 160 between the outer cover 110 and the outer surface 201 of the structure 200 for containing the viscous fluid 116, wherein the container 160 has an inner shape corresponding to the outer surface 201 of the structure 200 and an outer shape corresponding to the inner shape of the outer cover 110. The hydro-hook supported vibration damper assembly 100 may be disposed onto the structure 200 by securing the outer cover 110 to the container 160 and securing the container 160 to the outer surface 201 of the structure 200. It should be noted that this embodiment may also utilize the alternatives described above for the hydro-hook supported vibration damper assembly 100.

The above-described embodiments of the hydro-hook supported vibration damper assembly 100 according to the present invention may be combined to form other modified embodiments within the scope of the appended claims.

The hydro-hook supported vibration damper assembly 100 according to the present invention may be used in all types of semi-submerged or submerged

structures

200, 210, 220, 300 that may have underwater vibration problems, as shown and discussed throughout the specification. The dimensions of the

structures

200, 210, 220, 300 do not limit the design, nor the amplitude or operating frequency of the vibrations.

The hydro-hook supported vibration damper assembly 100 is particularly suitable for semi-submerged or submerged elongated primary

tubular structures

200, 210, 220, 300, such as elongated pipes in the form of drilling risers, where operation may cease for certain periods of the year due to high water currents. Adding the above-described hydrohook-supported vibration damper assembly 100 over a portion or the entire length of the riser can both reduce the VIV forces through the external anti-VIV geometry, and reduce the resonant vibrations (flow-induced vibrations (FIV), wave loads, etc.) from internal and external forces with the tuned mass damper effect of the hydrohook-supported vibration damper assembly 100.

Another example of a conduit to which the hydro-hook supported vibration damper assembly 100 according to the present invention is suitable is a jumper wire and a flexible loop. The jumpers and flex rings are flexible tubing that connects the wellhead to the manifold and must be flexible to make the connection and accommodate tolerances due to well growth, thermal expansion, positional errors, etc. It is well known that there are FIV problems with jumpers and flex rings due to high thrust from well flow, and that the hydraulic hook support vibration damper assembly 100 according to the present invention can alleviate these problems.

Other elongate subsea pipelines may be affected by FIV, VIV and flow induced pulsations (FLIP) simultaneously. As described above, vibrations from all forces can be mitigated by the hydro-hook supported vibration damper assembly 100 according to the present invention.

Other applications for which the hydro-hook supported vibration damper assembly 100 according to the present invention is suitable are structural members for submerged or

semi-submerged structures

200, 210, 220, 300, such as support structures for offshore platforms or wind turbines, where a minimum amount of material is desired, but structural integrity is critical due to dynamic and static loads. The addition of the hydro hook support vibration damper assembly 100 according to the present invention will reduce dynamic loads from waves, wind, ocean currents, etc., similar to the reduction of pipe vibration as previously described. Reducing the effect on the dynamic load of the wind turbine will also provide for a more power efficient operation of the wind turbine, since the variation in pitch can be reduced and therefore the wind turbine will have less movement with respect to the wind direction.

Other structures that would benefit from the use of the invention are nozzles, fresh water supplies, sea lines, tension legs (see fig. 27) and mooring lines (see fig. 28) (cables, wires, chains), and transport pipes or tubes of all kinds (for oil and gas, water, fish meal etc.).

Thus, the present invention will be applicable to all submerged or semi-submerged structures where vibration damping is required.

Variants

According to a variant of the invention, the hydrodynamic additional mass can be activated by a hydrohook-supported vibration damper assembly provided with an actuator acting as an active hydrohook-supported vibration damper assembly. According to the invention, this can be achieved by: the placement of the hydro hook support vibration damper assembly to a surface or side of a structure, an extension of a structure, a support structure for the structure, or a hydro hook support vibration damper support structure is accomplished rather than completely enclosing it as described above for certain embodiments. Alternatively, this may be achieved by: the outer covering is designed to have different hydrodynamic masses in different directions, thereby achieving different damping characteristics to meet the different eigenfrequencies that the structure, the extension of the structure, the support structure of the structure or the hydro-hook supported vibration damper support structure must have. In another alternative, this is achieved by using friction discs to increase damping.

Claims

1. A vibration damping method for a semi-submersible or submersible structure (200, 210, 220, 300), characterized by: hydrodynamic additional mass (m) by means of a hydraulic hook supporting a vibration damper assembly (100)_add) Separate from the semi-submerged or submerged structure (200, 210, 220, 300), the hydrohook supportsThe vibration damper assembly has spring and/or damper characteristics; and a hydrodynamic additional mass (m) to be separated_add) Used as a hydro hook to support a reaction mass in a vibration damper assembly (100).

2. Method according to claim 1, characterized in that the hydrodynamic additional mass (m) is separated by_add): an outer covering (110) is arranged partially or completely surrounding the structure (200, 210, 220, 300) and a damper space (111) is provided between the outer covering (110) and the structure (200).

3. The method of claims 1-2, wherein the damping coefficient is provided to the hydrahook support vibration damper assembly (100) by: the damper space (111) is sealed and the viscous fluid (116) is arranged in the damper space (111).

4. The method of claims 1-2, wherein the damping coefficient is provided to the hydrahook support vibration damper assembly (100) by: a magnet or magnet assembly (117) is arranged in the damper space (111) and a plate (118) is arranged on each side of the magnet or magnet assembly (117), the magnet or magnet assembly and the plate being arranged to the outer covering (110) and the structure (200, 210, 220, 300), respectively, and vice versa, to provide an alternating magnetic field.

5. The method of claims 1-2, wherein the damping coefficient is provided to the hydrahook support vibration damper assembly (100) by: -arranging an annular spacer (130) with a high friction sliding surface (131) to seal the damper space (111) and arrange the incompressible fluid in the damper space (111), or-arranging an annular spacer (130) with a low friction sliding surface (131) at each end of the outer cover (110) and arranging a magnet or magnet assembly (117) in the damper space (111) and a plate (118) on each side of the magnet or magnet assembly (117), the magnet or magnet assembly and the plate being arranged to the outer cover (110) and the structure (200, 210, 220, 300), respectively, or vice versa, to provide an alternating magnetic field.

6. The method of claims 1-2, wherein the coefficient of stiffness is provided to the hydrohook-supported vibration damper assembly (100) by: -arranging fastening means (119) extending between the inner periphery of the outer covering (110) and the outer periphery of the structure (200, 210, 220, 300).

7. The method of claims 1-2, wherein the coefficient of stiffness is provided to the hydrohook-supported vibration damper assembly (100) by: an elastomeric seal (112) is used at the end of the outer cover (110).

8. The method of claims 1-2, wherein the coefficient of stiffness is provided to the hydrohook-supported vibration damper assembly (100) by: one or more springs or spring assemblies (120) extending between the outer surface of the structure (200, 210, 220, 300) and the inner surface of the outer covering (110) are arranged in the damper space (111).

9. Method according to any of claims 2 to 8, characterized in that stiffness and/or damping is introduced in series with at least one spring element (112, 119, 120) and/or damping element (116, 117, 118) by using an outer covering (110) made of a rigid or flexible material.

10. Method according to any of the preceding claims, characterized in that in the longitudinal direction of the structure (200, 210, 220, 300) a number of hydraulic hook supporting vibration damper assemblies (100) are arranged to each other, which are separated by an annular spacer (130) with a high or low friction sliding surface (131) to provide a damping coefficient.

11. Hydraulic hook support vibrator for semi-submerged or submerged structures (200, 210, 220, 300)Dynamic damper assembly (100), characterized in that the hydrohook-supported vibration damper assembly (100) comprises at least one spring element (112, 119, 120) and/or damper element (116, 117, 118) arranged for hydrodynamically adding a mass (m) to the mass_add) Separating and adding a mass (m) of fluid power from a semi-submerged or submerged structure (200, 210, 220, 300)_add) Used as a hydro hook to support a reaction mass in a vibration damper assembly (100).

12. The hydrohook-supported vibration damper assembly (100) according to claim 11, wherein the hydrohook-supported vibration damper assembly (100) comprises an outer covering (110) arranged to partially or completely surround the structure (200, 210, 220, 300) and form a damper space (111) between the outer covering (110) and the structure (200, 210, 220, 300).

13. The hydrohook-supported vibration damper assembly (100) of claim 12, wherein the outer cover (110) is provided at its end with a seal (112) that seals against the structure (200, 210, 220, 300).

14. The hydrohook-supported vibration damper assembly (100) according to claims 11-13, wherein the at least one damper element (116) is formed by a layer (116) of viscous liquid arranged in a damper space (111).

15. The hydrohook-supported vibration damper assembly (100) according to claims 11-13, wherein the at least one damper element is formed by at least one magnet or magnet assembly (117) in the damper space (111) and a plate (118) arranged on each side of the at least one magnet or magnet assembly (117), which are arranged to the outer covering (110) and the structure (200, 210, 220, 300), respectively, or vice versa.

16. The hydrohook-supported vibration damper assembly (100) according to claim 12, wherein an annular spacer (130) with a high-friction sliding surface (131) is arranged on each side of the outer covering (110) and an incompressible fluid is arranged in the damper space (111); or an annular spacer (130) with a low-friction sliding surface (131) is arranged on each side of the outer covering (110), and at least one magnet or magnet assembly (117) is arranged in the damper space (111) and a plate (118) is arranged on each side of the at least one magnet or magnet assembly (117), which are arranged to the outer covering (110) and the structure (200, 210, 220, 300), respectively, or vice versa, to provide an alternating magnetic field.

17. The hydrohook-supported vibration damper assembly (100) according to claim 16, further comprising an inner layer or longitudinal spacer (132) disposed between the adhesive layer (116) and the structure (200, 210, 220, 300).

18. The hydrohook-supported vibration damper assembly (100) according to claim 12, wherein the hydrohook-supported vibration damper assembly (100) further comprises a fastening device (119) extending between an inner periphery of the outer covering (110) and an outer periphery of the structure (200, 210, 220, 300).

19. The hydrohook-supported vibration damper assembly (100) according to claim 13, wherein the seal (112) is formed of an elastomeric material.

20. The hydrohook-supported vibration damper assembly (100) according to claim 12, wherein the hydrohook-supported vibration damper assembly (100) further comprises one or more springs or spring assemblies (120) arranged in the damper space (111) extending between an outer periphery of the structure (200, 210, 220, 300) and an inner periphery of the outer covering (110).

21. Hydrohook-supporting vibration damper assembly (100) according to any one of claims 11-20, wherein several hydrohook-supporting vibration damper assemblies (100) are arranged to each other in the longitudinal direction of the structure (200, 210, 220, 300), which are separated by an annular spacer (130) provided with a high-friction or low-friction sliding surface (131).

22. The hydrohook-supported vibration damper assembly (100) of claim 12, wherein the outer cover (110) is formed or provided with fins (113), grids (114), spacers (115), or a combination thereof on its outer surface.

23. The hydrohook-supporting vibration damper assembly (100) according to any one of claims 12-22, wherein the outer cover (110) is formed of a rigid or flexible material to introduce stiffness and/or damping in series with the at least one spring element (112, 119, 120) and/or damping element (116, 117, 118).

24. Hydrohook-supporting vibration damper assembly (100) according to any one of claims 11-23, wherein the hydrohook-supporting vibration damper assembly (100) is divided into a plurality of sections (100a) provided with means (140) for mutual connection.